Generating node access information for a transaction accessing nodes of a data set index

ABSTRACT

Provided are a computer program product, system, and method for generating node access information for a transaction accessing nodes of a data set index. Pages in the memory are allocated to internal nodes and leaf nodes of a tree data structure representing all or a portion of a data set index for the data set. A transaction is processed with respect to the data set that involves accessing the internal and leaf nodes in the tree data structure, wherein the transaction comprises a read or write operation. Node access information is generated in transaction information, for accessed nodes comprising nodes in the tree data structure accessed as part of processing the transaction. The node access information includes a pointer to the page allocated to the accessed node prior to the transaction in response to the node being modified during the transaction.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a computer program product, system, andmethod for generating node access information for a transactionaccessing nodes of a data set index.

2. Description of the Related Art

A partitioned data set extended (PDSE) is a data set having an index andzero or more members. When adding new data for a new or existing member,the new data is appended sequentially to the end of the PDSE.

The PDSE index may be implemented in a tree data structure where pagesallocated to the PDSE data sets are assigned to implement internal nodesand leaf nodes representing the data set index. Each leaf noderepresents one of the members and provides information on the memberthat may be used to access the member. Each internal node has one ormore child leaf nodes. When a user seeks to access a member, the membername is presented and the tree is traversed to the internal node andleaf node representing the requested member using the member name as theindex key. Member data is only loaded into the memory when accessed.

There is a need in the art for improved techniques for managing pages inmemory implementing leaf and internal nodes of a data set index.

SUMMARY

Provided are a computer program product, system, and method forgenerating node access information for a transaction accessing nodes ofa data set index. Pages in the memory are allocated to internal nodesand leaf nodes of a tree data structure representing all or a portion ofa data set index for the data set, wherein the leaf nodes identify dataset members and the internal nodes are used to traverse the tree datastructure to access the leaf nodes. A transaction is processed withrespect to the data set that involves accessing the internal and leafnodes in the tree data structure, wherein the transaction comprises aread or write operation. Node access information is generated intransaction information, for accessed nodes comprising nodes in the treedata structure accessed as part of processing the transaction, whereinthe node access information includes a pointer to the page allocated tothe accessed node prior to the transaction in response to the node beingmodified during the transaction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment a computing environment.

FIG. 2 illustrates an embodiment of a data set.

FIG. 3 illustrates an embodiment of page information providinginformation on a page implementing a node of the data set index.

FIG. 4 illustrates an embodiment of a data set index having a tree datastructure.

FIG. 5 illustrates an embodiment of internal node information maintainedin a page implementing an internal node.

FIG. 6 illustrates an embodiment of leaf node information maintained inthe page implementing a leaf node.

FIG. 7 illustrates an embodiment of transaction information for atransaction opened on a data set.

FIG. 8 illustrates an embodiment of node access information fortransaction information for a transaction accessing the nodes of a dataset index.

FIG. 9 illustrates an embodiment of operations to open and process awrite transaction to a data set.

FIG. 10 illustrates an embodiment of operations to open and process aread transaction to a data set.

FIG. 11 illustrates an embodiment of operations to process notificationof invalidating/freeing a page.

FIG. 12 illustrates an embodiment of operations to roll back a writetransaction.

FIG. 13 illustrates an embodiment of an implementation of a computingsystem.

DETAILED DESCRIPTION

A challenge with PDSE data sets is the lack of structure andtransparency of the page buffering system. PDSE index page buffering isa non-deterministic system in which a pool of buffered pages representsthe current valid set of pages for the particular PDSE address space butwithout any relational or temporal referencing. This lack of temporaland relational referencing impedes diagnosis of index problems and thereconstruction of the history of a particular index page in the buffer.

Described embodiments provide techniques to address the lack of temporalreferencing and history information for data sets, such as PDSE datasets, having indexes represented in a tree data structure with nodes.When processing a transaction with respect to a data set that involvesaccessing a plurality of the nodes in the tree data structure,transaction information is generated that includes node accessinformation for accessed nodes comprising nodes in the tree datastructure accessed as part of processing the transaction. The nodeaccess information includes a pointer to the page allocated to theaccessed node prior to the transaction in response to the node beingmodified during the transaction. The node access information for anaccessed node may be generated when the accessed node is accessed aspart of processing the transaction so that the transaction informationlogs node access information for all node processing from when thetransaction is opened until the transaction is closed. The gatheredtransaction information including information on each node of a treeindex accessed while processing a transaction allows for rolling back atransaction and performance analysis at the buffer level for data sets.

FIG. 1 illustrates an embodiment of a computing environment. A pluralityof hosts (not shown) may submit read and write requests to a server 100to access data in data sets 200 in a storage 104. The server 100includes a processor 106 and a memory 108 having a connection managerprogram 110 to manage read and write access to the data sets 200 _(i).The connection manager 110 may load data set indexes 400 into the memoryfor the data sets 102 that are opened for access. A data set memorymanager 114 manages the use of pages 116 _(i) of data in a page buffer118 in the memory 108 that are allocated to the connection manager 110for data set operations. A specific number of pages 116 _(i) in a pagebuffer 118 may be allocated for data set operations. The pages 116 _(i)allocated for data sets remain allocated to a data set even if not used.If additional pages 116 are needed, the data set memory manager 114 mayrequest additional pages to be allocated for data set operations. A page116 _(i) may comprise a fixed sized page allocated to store the data setindexes 400 and data set members. The data set memory manager 114maintains page information 300 having information on pages 116 _(i)allocated to data sets.

The data set memory manager 114 may further maintain data settransaction lists 120 _(i), one for each data set 200 _(i), identifyingtransaction information instances 700 _(i), one for each transaction 122_(i) executed against one of the data sets 200 _(i). The transactioninformation instance 700 _(i) provides information on the transaction122 _(i) operations with respect to accessing the nodes of the data setindex 400 during execution of the transaction 122 _(i). An invalidateleast recently used (LRU) list 124 identifies pages 116 to invalidate,such as pages having been deallocated and available for use.

In one embodiment, the memory 108 may comprise a volatile ornon-volatile storage, such as a Dynamic Random Access Memory (DRAM),flash memory, Random Access Memory (RAM) or a non-volatile memory, e.g.,battery backed-up Random Access Memory (RAM), static RAM (SRAM),storage-class memory (SCM), etc., Phase Change Memory (PCM), resistiverandom access memory (RRAM), spin transfer torque memory (STM-RAM),conductive bridging RAM (CBRAM), etc.

The storage 104 may comprise a non-volatile storage, such as magnetichard disk drives, solid state storage device (SSD) comprised of solidstate electronics, EEPROM (Electrically Erasable Programmable Read-OnlyMemory), flash memory, flash disk, Random Access Memory (RAM) drive,storage-class memory (SCM), etc., Phase Change Memory (PCM), resistiverandom access memory (RRAM), spin transfer torque memory (STM-RAM),conductive bridging RAM (CBRAM), magnetic hard disk drive, optical disk,tape, etc. The data sets 200 _(i) may further be configured from anarray of devices, such as Just a Bunch of Disks (JBOD), Direct AccessStorage Device (DASD), Redundant Array of Independent Disks (RAID)array, virtualization device, etc.

The connection manager 110 and data set memory manager 114 may compriseone or more programs loaded into the memory 108 that are executed by theprocessor 106 or may be implemented in one or more hardware devices inthe server 100, such as in Application Specific Integrated Circuits(ASIC).

FIG. 2 illustrates an embodiment of an instance of a data set 200 _(i),which includes an index 400 used to access members 204 of the data set200 _(i). A member 204 comprises a range or extents of tracks. Incertain embodiments, the data sets 200 _(i) may comprise a PartitionedData Set Extended (PDSE), where new data is written to the end of thedata set and old versions of members are reused or deleted. Inalternative embodiments, the data sets 200 _(i) may comprise a type ofdata set other than a PDSE.

FIG. 3 illustrates an embodiment of page information 300 _(i) the dataset memory manager 114 uses to manage the pages 116 _(i) allocated fordata sets 200 _(i). The page information 300 _(i) for each page 116 _(i)indicates a page identifier (ID) 302; a memory location 304 in thememory 108 of the page 302; a data set 306 for which the page 300 _(i)is allocated; and a status 308 indicating whether the page 302 is freedor available, allocated to a node or member of a data set 200 _(i).

FIG. 4 illustrates an implementation of the data set index 400 as a treedata structure having internal nodes 500 (also known as non-leaf nodes)and leaf nodes 600. There may be one page 116 _(i) in the memory 108allocated to each node, leaf and internal. Each leaf node 600 _(i) mayprovide information on one or more members 204 of a data set 200 _(i)used to access the members 204. The internal nodes 500 include one ormore keys and links to one or more leaf nodes 600. The keys of theinternal nodes 500 are used to traverse the tree structure representingthe data set memory index 400 to access the leaf nodes 600 having theinformation on data set members 204. The keys in the internal nodes 500used to access the leaf nodes 600 may comprise characters or characterstrings for member 204 names. Alternatively, the keys may comprise othervalues used to access leaf nodes 600 for members 204 being accessed.

FIG. 5 illustrates an embodiment of information in a data structuremaintained for an instance of an internal node 500 _(i), which may beimplemented as a page 116 _(i) in the memory 108, including a nodeidentifier (ID) 502; a parent node 504 in the tree data structure index400 comprising the root node or another internal node; for each of theone or more child nodes of the node 502, a child pointer 506 ₁ . . . 506n pointing to the child node of the internal node 502 and child keys 508₁ . . . 508 _(n) used to determine the child node pointer to select atthe internal node 502 to traverse; and a lock 510 indicating a type oflock, if any, set for the node 502.

FIG. 6 illustrates an embodiment of an instance of a leaf node 600 _(i),which may be implemented as a page 116 _(i) in the memory 108, includinga node ID 602 identifying the leaf node; one or more data set memberdescriptors 604 identifying data set members 204 assigned to the leafnode 602 if any; and a lock 606 indicating a type of lock, if any, setfor the leaf node 602.

In one embodiment, the members 204 may have member names used to indexthe members 204 in the tree structure. For instance, the internal nodes500 may have keys related to characters in a member name that are usedto determine a link to the appropriate leaf node page 600 based on themember name when searched. An internal node 500 _(i), may have a numberof child leaf nodes that is one greater than the number of member namekeys maintained in the internal node to index the child leaf nodes.

FIG. 7 illustrates an embodiment of an instance of transactioninformation 700 _(i) maintained for one transaction, and includes: atransaction information identifier (ID) 702; a data set 704 to which thetransaction 702 is directed; a transaction identifier (ID) 706 of thetransaction; a transaction type 708, such as a read or write operation;a lifespan 710 indicating a duration since the transaction information702 was created; and one or more node access information instances 800_(i) providing information on each index node 500 _(i), 600 _(i)accessed during operations implementing the transaction 702.

FIG. 8 illustrates an embodiment of an instance of node accessinformation 800 _(i) providing information on each node access thatoccurs during execution of a transaction 122 _(i), including a sequencenumber 802 of access of the node 804 to indicate the order in which thecurrent node access occurs; a node ID 804 identifying the node in thedata set index being accessed; a request type 806 of the access, such asread or write/modify at the node 804; a timestamp 808 at which the node804 was accessed; an I/O required indicator 810, which indicates whetherthe page allocated to the node 804 had to be staged from the storage 104to the page buffer 118; a page pointer 812 pointing to a previous pageallocated to the node 804 that was deallocated if the node was modified;and a page valid flag 814 indicating whether the deallocated pageaddressed by the pointer 812 is still valid in the page buffer 118 orhas been invalidated and freed for allocation to another node or member.In certain embodiments, if the node 804 has not had a page modified anddeallocated or the page addressed by the pointer 812 has beeninvalidated, then the page pointer 812 may have a null value.

Additional flags and information may be provided for the informationdescribed with respect to FIGS. 2, 3, and 5-8.

FIG. 9 illustrates an embodiment of operations performed by the data setmemory manager 114 when a write transaction 122 _(w) is executed togenerate node access information 800 _(i) for transaction information700 _(i) for the write transaction 122 _(W) being executed. Uponreceiving (at block 900) an open for a write transaction 122 _(W) to adata set 200 _(i) with respect to data set members 204, the data setmemory manager 114 creates (at block 902) transaction information 700_(i) for the write transaction 122 _(w) and sets (at block 904) asequence number (s) to zero. Upon processing (at block 906) a node inthe data set index 400 tree for the data set to which the transaction122 _(i) is directed, the data set memory manager 114 creates (at block908) node access information 900 _(S), where s is the sequence number,in the transaction information 700 _(i) for the processed nodeindicating the sequence number 802; the node identifier 804 of theaccessed node; a request type 806 for the node access, i.e., read ormodified (added, deleted, or updated); a timestamp 808 the node isprocessed; and whether I/O required 810 to the storage 104 to retrievethe page 116 _(i) implementing the accessed node.

If (at block 910) the processed node is being added, then the data setmemory manager 114 allocates (at block 912) a page 116 _(i) to theinternal 500 i or leaf 600 i node being added and sets (at block 916)the page pointer 812 to invalid and the page valid flag 814 to indicateinvalid, i.e., the page pointer 812 for the previous page for the nodedoes not point to a valid page 116. If (at block 910) the processed nodeis not being added and if (at block 918) the accessed node is modifiedas part of executing the transaction 122 _(w), then the node content inthe current page 116 _(c) for the node is read (at block 920). The pagepointer 812 is set (at block 922) to the current page 116 _(c) for thenode and the current page 116 is deallocated (at block 924) and added tothe invalidate LRU list 124. A separate process of the data set memorymanager 114 processes pages on the invalidate LRU list 124 to invalidateand free pages in the LRU list 124 to make available for use for nodesor members for a data set. A new page 116 _(N) for the modified node isallocated (at block 926) and the modified data for the node, includingthe read data for the node with the modifications from the transaction122 _(W), is written (at block 928) to the allocated new page 116 _(N).

After completing the write (at block 928) or if the node is not modified(from the no branch of block 918) or after setting the page pointer toinvalid (at block 916), control proceeds to block 930. If (at block 930)the write transaction 122 _(W) is not completed, then the sequencenumber (s) is incremented (at block 932) and control proceeds to block906 to process a next node during execution of the write transaction 122_(W). If (at block 930) the transaction 122 _(W) is completed, then thetransaction information 700 _(i) is indicated (at block 934) in a dataset transaction list 120 _(i) for the data set 200 _(i) subject to theprocessed write transaction 122 _(W) and the write transaction 122 _(W)is closed (at block 936).

FIG. 10 illustrates an embodiment of operations performed by the dataset memory manager 114 when a read transaction 122 _(R) is executed togenerate node access information 800 _(i) for transaction information700 _(i) for the read transaction 122 _(R) being executed. Uponreceiving (at block 1000) an open for a read transaction 122 _(R) to adata set with respect to data set members 204, the data set memorymanager 114 creates (at block 1002) transaction information 700 _(i) forthe read transaction 122 _(R) and sets (at block 1004) a sequence number(s) to zero. Upon processing (at block 1006) a node in the data setindex 400 tree for the data set to which the read transaction 122 _(R)is directed, the data set memory manager 114 creates (at block 1008)node access information 800 _(S), where s is the sequence number, in thetransaction information 700 _(i) for the processed node indicating thesequence number 802; the node identifier 804 of the accessed node; aread request type for the node access; a timestamp 808 the node isprocessed; and whether I/O is required 810 to the storage 104 toretrieve the page 116 _(S) implementing the accessed node to retrievethe page implementing the node.

After completing the processing of the node, if (at block 1010) the readtransaction 122 _(R) is not completed, then the sequence number isincremented (at block 1012) and control proceeds to block 1006 toprocess a next node during execution of the read transaction 122 _(R).If (at block 1010) the read transaction 122 _(R) is completed, then readtransaction 122 _(R) is closed (at block 1014) and the transactioninformation 700 _(i) generated for the closed read transaction 700 _(i)is deleted (at block 1016).

With the operations of FIGS. 9 and 10, simultaneously when processing anode in a data set index during execution of a write or readtransaction, node access information 800 _(i) is created for transactioninformation 700 _(i) for the transaction 122 _(i) being executed toprovide information on operations performed at the nodes duringexecution of the transaction _(122i). Further, with write transactions,the page deallocated from a node when modifying the node and writing toa new page is indicated in a pointer 812 in the node access information800 _(i) to provide the previous state for the node after modifying anode.

FIG. 11 illustrates an embodiment of operations performed by the dataset memory manager 114 when a deallocated page from a node isinvalidated or freed to be available for subsequent use for a node ormember. Upon receiving (at block 1100) notification that a deallocatedpage 116 _(I) in the invalidate page LRU list 124 is invalidated orfreed for later use, the data set memory manager 114 determines (atblock 1102) whether there is node access information 800 _(i) having apointer to the invalid/freed page 116 _(I) in one transactioninformation instance 700 _(i) indicated in the data transaction list 120_(i) for the data set 200 _(i). If (at block 1102) one of the nodeaccess information instances 800 _(i) points to the invalidated/freedpage 116 _(I), then the page valid flag 814 is set (at block 1106) inthat instance 800 _(i) to indicate invalid. If (at block 1108) all theprevious deallocated pages identified by pointers 812 in all the nodeaccess information instances 800 _(i) for the determined transactioninformation 700 _(i) are invalid, i.e., the page valid flag 814 for allthe node access information instances 800 _(i) is invalid, then thedetermined transaction information 700 _(i) is deleted and removed (atblock 1110) from the data set transaction list 120 _(i). If (at block1108) there are some node access information instances 800 _(i) stillhaving valid deallocated pages for the transaction, then control ends.

With the described embodiments of FIG. 11, the transaction information700 _(i) for a write transaction is deleted when all the deallocatedpages identified by pointers 812 in the node access information 800 _(i)are invalidated. In a further embodiment, the transaction information700 _(i) for a write transaction 122 _(i) may be deleted when thelifespan 710 of the transaction information 700 _(i) exceeds a thresholdlifespan. In a yet further embodiment, transaction information 700 _(i)may be deleted if space used by transaction information 700 _(i) fordifferent write transactions exceeds a storage threshold for transactioninformation.

FIG. 12 illustrates an embodiment of operations performed by the dataset memory manager 114, or other component, to roll back a writetransaction 122 _(W). The roll-back operation may be initiated inresponse to a user request if a write transaction fails or to reverse orrecover data inadvertently overwritten. The user may specify the writetransaction 122 _(W) and associated transaction information 700 _(W) toroll back. Alternatively, the roll-back operation may automaticallyoccur in response to the write transaction failing. Upon initiating (atblock 1200) the roll-back operation, the data set memory manager 114determines (at block 1202) the transaction information 700 _(W) for thetransaction 122 _(W) to roll back. For each node access informationinstance 800 _(i) for a modified node having a valid buffered page(e.g., with a page valid flag 814 indicating valid), processed accordingto a reverse order of the sequence numbers 802 of the node accessinformation, the data set memory manager 114 deallocates (at block 1204)the current page for the modified node and allocates the page indicatedby the pointer 812 in the node transaction information to the modifiednode to return the node to the pre-transaction state.

With the described operations of FIG. 12, a write transaction may berolled back by replacing the current pages for modified nodes in thedata set index 400 with the page indicated by the pointer 812 for thosenode access information instances 800 _(i) having the valid flag 814indicating a valid previous version of a page 116 _(i) for the node.

In further embodiments, the transaction information 700 _(i) may be usedto determine whether to commit a page and write to memory. If onetransaction completes, before committing modified pages for nodes in thememory 108 to the storage 104, the data set memory manager 114 mayprocess transaction information 700 _(i) as indicated in the data settransaction list 120 _(i) for the data set to which the page isallocated to determine whether the transaction information 700 _(i) forany other open transactions have node access information 800 _(i) forthe node allocated the page being considered to commit. In such case,that other transactions are performing operations with respect to thenode allocated the page being considered for commit, the commit of thatpage may be delayed until there are no more open transactions processingthe node allocated the page to commit. This deferral of the commitstreamlines operations by avoiding have to perform another read afterthe commit to access the page from the storage 104 when another opentransaction accesses that page to access the node implemented in thatpage. Deferring commit until all open transactions accessing the nodeimplemented in that page have completed reduces the need to stage thepage for the node back into memory 108 after the page for the node iscommitted and destaged to the storage 104

Described embodiments provide techniques to gather history informationon node accesses during a read or write transaction by generating, intransaction information, node access information for accessed nodescomprising nodes in the tree data structure accessed as part ofprocessing the transaction. The node access information includes apointer to the page allocated to the accessed node prior to thetransaction in response to the node being modified during thetransaction. The transaction information may be used to analyze failedread or write transactions or roll-back a write transaction.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Smalltalk, C++ or the like,and conventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The server 100 of FIG. 1 may be implemented in one or more computersystems, such as the computer system 1302 shown in FIG. 13. Computersystem/server 1302 may be described in the general context of computersystem executable instructions, such as program modules, being executedby a computer system. Generally, program modules may include routines,programs, objects, components, logic, data structures, and so on thatperform particular tasks or implement particular abstract data types.Computer system/server 1302 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 13, the computer system/server 1302 is shown in theform of a general-purpose computing device. The components of computersystem/server 1302 may include, but are not limited to, one or moreprocessors or processing units 1304, a system memory 1306, and a bus1308 that couples various system components including system memory 1306to processor 1304. Bus 1308 represents one or more of any of severaltypes of bus structures, including a memory bus or memory controller, aperipheral bus, an accelerated graphics port, and a processor or localbus using any of a variety of bus architectures. By way of example, andnot limitation, such architectures include Industry StandardArchitecture (ISA) bus, Micro Channel Architecture (MCA) bus, EnhancedISA (EISA) bus, Video Electronics Standards Association (VESA) localbus, and Peripheral Component Interconnects (PCI) bus.

Computer system/server 1302 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 1302, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 1306 can include computer system readable media in theform of volatile memory, such as random access memory (RAM) 1310 and/orcache memory 1312. Computer system/server 1302 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 1313 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 1308 by one or more datamedia interfaces. As will be further depicted and described below,memory 1306 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 1314, having a set (at least one) of program modules1316, may be stored in memory 1306 by way of example, and notlimitation, as well as an operating system, one or more applicationprograms, other program modules, and program data. Each of the operatingsystem, one or more application programs, other program modules, andprogram data or some combination thereof, may include an implementationof a networking environment. The components of the computer 1302 may beimplemented as program modules 1316 which generally carry out thefunctions and/or methodologies of embodiments of the invention asdescribed herein. The systems of FIG. 1 may be implemented in one ormore computer systems 1302, where if they are implemented in multiplecomputer systems 1302, then the computer systems may communicate over anetwork.

Computer system/server 1302 may also communicate with one or moreexternal devices 1318 such as a keyboard, a pointing device, a display1320, etc.; one or more devices that enable a user to interact withcomputer system/server 1302; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 1302 to communicate withone or more other computing devices. Such communication can occur viaInput/Output (I/O) interfaces 1322. Still yet, computer system/server1302 can communicate with one or more networks such as a local areanetwork (LAN), a general wide area network (WAN), and/or a publicnetwork (e.g., the Internet) via network adapter 1324. As depicted,network adapter 1324 communicates with the other components of computersystem/server 1302 via bus 1308. It should be understood that althoughnot shown, other hardware and/or software components could be used inconjunction with computer system/server 1302. Examples, include, but arenot limited to: microcode, device drivers, redundant processing units,external disk drive arrays, RAID systems, tape drives, and data archivalstorage systems, etc.

The terms “an embodiment”, “embodiment”, “embodiments”, “theembodiment”, “the embodiments”, “one or more embodiments”, “someembodiments”, and “one embodiment” mean “one or more (but not all)embodiments of the present invention(s)” unless expressly specifiedotherwise.

The terms “including”, “comprising”, “having” and variations thereofmean “including but not limited to”, unless expressly specifiedotherwise.

The enumerated listing of items does not imply that any or all of theitems are mutually exclusive, unless expressly specified otherwise.

The terms “a”, “an” and “the” mean “one or more”, unless expresslyspecified otherwise.

Devices that are in communication with each other need not be incontinuous communication with each other, unless expressly specifiedotherwise. In addition, devices that are in communication with eachother may communicate directly or indirectly through one or moreintermediaries.

A description of an embodiment with several components in communicationwith each other does not imply that all such components are required. Onthe contrary a variety of optional components are described toillustrate the wide variety of possible embodiments of the presentinvention.

When a single device or article is described herein, it will be readilyapparent that more than one device/article (whether or not theycooperate) may be used in place of a single device/article. Similarly,where more than one device or article is described herein (whether ornot they cooperate), it will be readily apparent that a singledevice/article may be used in place of the more than one device orarticle or a different number of devices/articles may be used instead ofthe shown number of devices or programs. The functionality and/or thefeatures of a device may be alternatively embodied by one or more otherdevices which are not explicitly described as having suchfunctionality/features. Thus, other embodiments of the present inventionneed not include the device itself.

The foregoing description of various embodiments of the invention hasbeen presented for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed. Many modifications and variations are possible in lightof the above teaching. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto. The above specification, examples and data provide acomplete description of the manufacture and use of the composition ofthe invention. Since many embodiments of the invention can be madewithout departing from the spirit and scope of the invention, theinvention resides in the claims herein after appended.

What is claimed is:
 1. A computer program product for maintaininginformation on pages in a memory used for data in a data set stored in astorage, the computer program product comprising a computer readablestorage medium having computer readable program code embodied thereinthat executes to perform operations, the operations comprising:processing a write transaction with respect to a data set member of thedata set, comprising at least one track in the storage, that involvesaccessing internal nodes and leaf nodes in a tree data structurerepresenting the data set, wherein the leaf nodes identify data setmembers and the internal nodes are used to traverse the tree datastructure to access the leaf nodes; generating node access informationfor nodes accessed during the write transaction in the tree datastructure indicating whether the accessed nodes were modified, whereinthe node access information includes information on modifications tointernal nodes and leaf nodes; and including the node access informationfor the accessed nodes in transaction information for the writetransaction, wherein the transaction information for the writetransaction has node access information indicating modifications tointernal nodes and leaf nodes that were accessed during the writetransaction and changed as a result of the write transaction.
 2. Thecomputer program product of claim 1, wherein the operations furthercomprise: including the transaction information of the node accessinformation for the accessed nodes in a data set transaction listincluding transaction information for multiple write transactions to thedata set.
 3. The computer program product of claim 1, wherein thetransaction information indicates a lifespan threshold, wherein theoperations further comprise: deleting the transaction information andincluded node access information in response to a lifespan of thetransaction information exceeding the lifespan threshold.
 4. Thecomputer program product of claim 1, wherein the operations furthercomprise: modifying an accessed node as part of the write transaction;and allocating a new page for the modified accessed node for write datafrom the write transaction.
 5. The computer program product of claim 4,wherein the operations further comprise: deallocating a page allocatedto the modified accessed node before the write transaction to beavailable for reuse as an unallocated page; adding the deallocated pageto an invalidate list from which pages are invalidated and freed; andupdating a pointer in the node access information for the deallocatedpage to indicate the deallocated page and indicate that the deallocatedpage is valid.
 6. The computer program product of claim 5, wherein theoperations further comprise: indicating the deallocated page addressedby the pointer in the node access information for a node as invalid inresponse to freeing the page when processing the invalidate list.
 7. Thecomputer program product of claim 5, wherein the operations furthercomprise: initiating an operation to roll back the write transaction;and for node access information for a modified node indicating that thedeallocated page is valid, deallocating a current page for the modifiednode and allocate the page indicated by the pointer in the node accessinformation to the modified node.
 8. A system in communication with astorage, comprising: a processor; a memory having pages used for data ina data set stored in the storage; computer readable program code in thememory executed by the processor to perform operations, the operationscomprising: processing a write transaction with respect to a data setmember of the data set, comprising at least one track in the storage,that involves accessing internal nodes and leaf nodes in a tree datastructure representing the data set, wherein the leaf nodes identifydata set members and the internal nodes are used to traverse the treedata structure to access the leaf nodes; generating node accessinformation for nodes accessed during the write transaction in the treedata structure indicating whether the accessed nodes were modified,wherein the node access information includes information onmodifications to internal nodes and leaf nodes; and including the nodeaccess information for the accessed nodes in transaction information forthe write transaction, wherein the transaction information for the writetransaction has node access information indicating modifications tointernal nodes and leaf nodes that were accessed during the writetransaction and changed as a result of the write transaction.
 9. Thesystem of claim 8, wherein the operations further comprise: includingthe transaction information of the node access information for theaccessed nodes in a data set transaction list including transactioninformation for multiple write transactions to the data set.
 10. Thesystem of claim 9, wherein the transaction information indicates alifespan threshold, wherein the operation further comprises: deletingthe transaction information and included node access information inresponse to a lifespan of the transaction information exceeding thelifespan threshold.
 11. The system of claim 9, wherein the operationsfurther comprise: modifying an accessed node as part of the writetransaction; and allocating a new page for the modified accessed nodefor write data from the write transaction.
 12. The system of claim 11,wherein the operations further comprise: deallocating a page allocatedto the modified accessed node before the write transaction to beavailable for reuse as an unallocated page; adding the deallocated pageto an invalidate list from which pages are invalidated and freed; andupdating a pointer in the node access information for the deallocatedpage to indicate the deallocated page and indicate that the deallocatedpage is valid.
 13. The system of claim 12, wherein the operationsfurther comprise: indicating the deallocated page addressed by thepointer in the node access information for a node as invalid in responseto freeing the page when processing the invalidate list.
 14. The systemof claim 12, wherein the operations further comprise: initiating anoperation to roll back the write transaction; and for node accessinformation for a modified node indicating that the deallocated page isvalid, deallocating a current page for the modified node and allocatethe page indicated by the pointer in the node access information to themodified node.
 15. A method for maintaining information on pages in amemory used for data in a data set stored in a storage, comprising:processing a write transaction with respect to a data set member of thedata set, comprising at least one track in the storage, that involvesaccessing internal nodes and leaf nodes in a tree data structurerepresenting the data set, wherein the leaf nodes identify data setmembers and the internal nodes are used to traverse the tree datastructure to access the leaf nodes; generating node access informationfor nodes accessed during the write transaction in the tree datastructure indicating whether the accessed nodes were modified, whereinthe node access information includes information on modifications tointernal nodes and leaf nodes; and including the node access informationfor the accessed nodes in transaction information for the writetransaction, wherein the transaction information for the writetransaction has node access information indicating modifications tointernal nodes and leaf nodes that were accessed during the writetransaction and changed as a result of the write transaction.
 16. Themethod of claim 15, further comprising: including the transactioninformation of the node access information for the accessed nodes in adata set transaction list including transaction information for multiplewrite transactions to the data set.
 17. The method of claim 15, furthercomprising: modifying an accessed node as part of the write transaction;and allocating a new page for the modified accessed node for write datafrom the write transaction.
 18. The method of claim 17, furthercomprising: deallocating a page allocated to the modified accessed nodebefore the write transaction to be available for reuse as an unallocatedpage; adding the deallocated page to an invalidate list from which pagesare invalidated and freed; and updating a pointer in the node accessinformation for the deallocated page to indicate the deallocated pageand indicate that the deallocated page is valid.
 19. The method of claim18, further comprising: indicating the deallocated page addressed by thepointer in the node access information for a node as invalid in responseto freeing the page when processing the invalidate list.
 20. The methodof claim 18, further comprising: initiating an operation to roll backthe write transaction; and for node access information for a modifiednode indicating that the deallocated page is valid, deallocating acurrent page for the modified node and allocate the page indicated bythe pointer in the node access information to the modified node.